Importance

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Abstract

A robot calibration system for calibration of a workpiece handling robot relative to a station. The workpiece handling robot includes a sensor mounted on an end effector. The robot calibration system also includes a target, which in coordination with the sensor, allows a control system to determine a center of the target. The target is a wafer in the shape of a disk. A pattern is on at least one side of the workpiece, preferably on a bottom side of the target. The pattern comprises alternating black and white areas. The workpiece handling robot is placed in front of the station which includes a cassette mounted thereon. The cassette has a support surface which supports the target. Once the z-height of the end effector is established with the end effector being in close proximity to a lowermost support surface of the cassette, the end effector proceeds to move in a search pattern searching the pattern for transition points from black to white areas. The control system stores these transition points and uses the transition points in an algorithmic equation to determine the center of the target. Once the center of the target has been identified, the control system knows the spacial relation between the robot and the station, and in particular the position of the workpieces at the station. The station may thereafter be loaded with workpieces and processed accordingly.

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First Claim